MBE Growth of GaAs on Porous Silicon
- PDF / 2,040,467 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 35 Downloads / 222 Views
MBE GROWTH OF GaAs ON POROUS SILICON 2 T. L. Lir *, L. SadwickI, It. L. WangI S. S. RheeI, Y. C KaoI, R. Hull , C. W. Nieh , D. N. Jamieson," J. K. Liu4, and M-A. Nicolet3 1. Department of Electrical Engineering, University of California, Los Angeles, CA 2. Hewlett Packard Research Laboratory, Palo Alto, CA 3. California Institute of Technology, Pasadena, CA 4. Jet Propulsion Laboratory, Pasadena, CA. * Present address: Jet Propulsion Laboratory, Pasadena, CA
ABSTRACT GaAs layers have been grown on porous silicon (PS) substrates by molecular beam epitaxy. No surface morphology deterioration was observed onGaAs-on-PS layers in spite of the roughness of PS. A 10% Rutherford backscattering spectroscopy (RBS) channeling minimum yield for GaAs-on-PS layers as compared to 16% for GaAs-on-Si layers grown under the same condition indicates a possible improvement of crystallinity when GaAs is grown on PS. Transmission electron microscopy (TEM) reveals that the dominant defects in the GaAs-on-PS layers are microtwins and stacking faults, which originate from the GaAs/PS interface. GaAs is found to penetrate into the PS layers. 1. INTRODUCTION In the last few years, great progress has been made in the epitaxial growth of GaAs layers on Si substrateS.11-31 The heteroepitaxial growth of GaAs on Si has the prospect of monolithic integration of GaAs devices with Si-base integrated circuits.[4] However, the 4% mismatch between GaAs and Si generates a large density of misfit dislocations. The problem is exacerbated by the large difference in the thermal expansion coefficients between GaAs and Si which results in a very large post-growth tensile stress in the GaAs layers. Several approaches have been utilized to suppress the propagation of threading dislocations from the GaAs/Si interface, such as growth of a strained InGaAs/GaAs superlatttice buffer layer,[51 and the use of a misoriented Si substrate. 1,51 However, the total defect density of epitaxial GaAs layers grown on Si substrate is much higher than that of bulk GaAs crystalj.1,51 Recently, a possible approach for growing dislocation-free lattice-mismatched heteroepitaxial layers on small seed pads of lateral dimension L, having a uniform crystal orientation over the entire substrate wafer, has been proposed by Luryi et al.[61 It was proposed that when L < Lmin , which is about 200 A for GaAs, the entire elastic stress in the epitaxial films will be accommodated without dislocations. Thus dislocation-free GaAs films might be epitaxially grown on a silicon substrate provided the lattpr surface is patterned with pads of a lateral dimension less than 200 A, separated by trenches of Lmi n - 65 A. However, this probably can not be achieved by any -lithography. Porous silicon (PS) substrates provide surface pads with dimensions ranging from 30 to 100 A and thus can be used as the starting substrate for the epitaxial growth of GaAs.[7] PS has been utilized for molecular
Mat- Res. Soc. Symp. Proc. Vol. 91. 1987 Materials Research Society
114
Figure 1. Surface morphology of the G
Data Loading...
